In the manufacture of packing containers for different types of contents methods and machines are used which convert packing material to finished packing containers, which are filled with the desired contents and closed. In the foodstuff industry, especially in the packaging of dairy products such as milk and the like, machines are used which convert packing container blanks in web or sheet form (possibly partly preformed and provided with opening arrangements or the like), fill them with the required quantity of contents and close them in liquid-tight manner.
A known machine (U.S. Pat. No. 3,785,113) for carrying out this process consists of a first part for the conversion of the packing container blanks to fillable packing containers and a second part for the filling and sealing and possibly final shaping of the packing containers. The first part comprises magazines for prefabricated packing container blanks, mandrel wheels on which the blanks are placed, and sealing and forming elements so as to form a liquid-tight base on each packing container blank. Subsequently the blanks are transferred to the second part of the machine and, more particularly, to conveyors which by means of intermittent advance move the blanks between different processing stations where they are filled with contents, the tops are formed and they are closed.
Machines of this type can provide the desired capacity if they are given the desired number of conveyors or production lines (mandrel wheels and conveyors) and, beside the said example with two production lines, it is also possible in larger machines to use three, four or even more production lines. This is done in that the desired number of production lines is placed parallel in a joint machine frame, each production line being provided with all parts associated with the production lines. However, generally a common electric and control system together with a common driving unit are employed.
When a packing machine of this type with two or more jointly driven production lines is used, however, certain disadvantages make themselves felt. Since each production line is driven intermittently, so that the packing containers transported in the conveyors are momentarily stopped at each station for filling, closing etc., an extremely varying load will be placed on the driving unit of the machine, and when the machine comprises two or more production lines arranged in parallel which are driven jointly in cycle with each other, these varying loads will become so great that they not only cause disadvantages in the form of increased power requirement, noise etc., but also bring about greatly increased wear of the driving unit and make necessary an appreciable overdimensioning of the same. The intermittent driving of all production lines in cycle with each other also means that the different processing stations will operate in cycle and thus cause substantial peaks in their requirement of electric power, hot air and the like.